TYPO3 Fluid flexible counter/iterator (count not every step) #TYPO3 #Fluid

FluidTemplate.html

<div xmlns="http://www.w3.org/1999/xhtml" lang="en"
     xmlns:f="http://typo3.org/ns/TYPO3/Fluid/ViewHelpers"
     xmlns:flux="http://typo3.org/ns/FluidTYPO3/Flux/ViewHelpers"
     xmlns:v="http://typo3.org/ns/FluidTYPO3/Vhs/ViewHelpers">

  <div>
  {namespace v=FluidTYPO3\Vhs\ViewHelpers}
    <v:variable.set name="i" value="0" />
    <f:for each="{array}" as="elem" iteration="iterator">
      val: {i} <br>
      <f:if condition="{elem.field}">
        <v:variable.set name="i" value="{v:math.sum(a: '{i}', b: '1')}" />
      </f:if>
    </f:for>
  </div>
  
</div>